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ON THE AFFINITIES OF C^NOLESTES. 

 [Marsupiaha]. 



By R. Broom, M.D., C.M.Z.S., Corresponding Member. 



In 1895, Oldfield Thomas described the remarkable South 

 iVnierican iiiarsupial, < 'it imh st( s : and ^avc reasons for believ- 

 ing that it represented a new type of Diprotodontia, and 

 apparently a living representative of a group previously 

 known by a few extinct forms. 



With regard to its affinities, Thomas considered that it is 

 closely allied to none of the living forms, but that it is more 

 nearly related to the existing marsupials of Australia, than 

 to those of America. "It is," he adds, "clearly a Diproto- 

 dont, as not only does it possess the characteristic develop- 

 ment of the lower incisors, but even the molars resemble 

 ''most closely in structure those of certain members of the 

 family rhalanyeridce, while being wholly unlike those of the 

 typical Polyprotodonts. From all of the existing Diproto- 

 donts, however, apart from its habitat and numerous detailed 

 differences, Ccenolestes is at once distinguished by its not 

 being syndactylous, a character which is always considered 

 as of family rank. . It forms, therefore, among existing 

 Marsu])ials a ])eculiar Family, and one which in America 

 represents the Diprotodonts of Australia, just as the 

 DidelphyifUe do the Polyprotodonts." 



In 1896, I had an opportunity, through the kindness of 

 Mr. Thomas, of examining the type-skull ; and I then came 

 to the conclusion that Ccenolestes was much more nearly allied 

 to the American Polyprotodonts than to the Australian 

 Diprotodonts. When dealing with the aflBnities and habits 

 of Thijlacoleo, in a paper published in 1898, I gave a diagram 

 of what I regarded as the phylogenetie relationships of the 



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